There is a substantial literature indicating that religiousness is related to measures of physical and mental health, as well as to longevity, and to measures of adjustment to aging. These relations most often are interpreted as indicative of a protective effect of religiousness, and there are many hypothesized mechanisms for this effect. Causal modeling of these mechanisms appears to be the next stage of development in this literature. There are several fundamental issues, however, that different researchers have recognized as basic to our understanding and interpretation of relations between religion and health, but that have yet to be systematically explored. These issues concern whether the scale of a common measure of religiosity, attendance, results in attenuation of relations with health variables, whether the form of the relation between religious involvement and health is linear or non-linear, whether there are moderators, such as denomination, of that relation, whether the relation is generalizable across religions and cultures, and whether religion, itself, is a moderator of the relation between objective and subjective health variables. This last issue has particular relevance for understanding the relation between subjective health and mortality among the elderly. The first issues result in questions concerning the appropriateness of linear structural models, because they challenge the assumptions of interval measurement, linearity, and additivity. Generally, the effect of inappropriate scaling and erroneous assumptions about the form of the relation between variables is that the magnitude of effects is attenuated and interpretations of relations are distorted. There is evidence, in this literature, of both non-linearity and non-additivity. The proposed research addresses each of these issues in a systematic way using multiple national and international data sets with large representative samples. Exploratory work will be conducted with one or two data sets, and then findings will be tested on several others. The most fundamental issue, the measurement of variables indicating religiosity, will be addressed first and findings will be incorporated into approaches to subsequent issues. When findings indicate that general linear model assumptions are not appropriate, both traditional analytic procedures and potentially more appropriate procedures, such as latent class analysis, will be used to determine the impact of violations of those assumptions, and to assess differences in interpretations that may result from the use of different procedures. The goal of this pilot project is to provide a foundation for a long- range program of research, developing multifactorial causal models of the complex interrelations of religion and health across the lifespan.